Reconstructing Indian monsoon strength in the Bay of Bengal during the Pliocene M2 event; estimation of paleosalinity levels

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doi: 10.1130/abs/2017SE-290486
Author(s): Steele, Kristen L.; Dowsett, Harry J.; Robinson, Marci M.; St. John, Kristen E.
Author Affiliation(s): Primary:
James Madison University, Department of Geology and Environmental Science, Harrisonburg, VA, United States
Other:
U. S. Geological Survey, United States
Volume Title: Geological Society of America, Southeastern Section, 66th annual meeting
Source: Abstracts with Programs - Geological Society of America, 49(3); Geological Society of America, Southeastern Section, 66th annual meeting, Richmond, VA, March 30-31, 2017. Publisher: Geological Society of America (GSA), Boulder, CO, United States. ISSN: 0016-7592 CODEN: GAAPBC
Note: In English
Summary: During the later part of the Pliocene Epoch global mean annual temperature was 2-3°C warmer than today, making this interval an excellent "process analogue" for climatic conditions projected for the end of this century. In many parts of Asia, particularly the Indo-Myanmar region, Southwest summer monsoon precipitation is closely linked to the well-being of the human population. Recent variability in the monsoon system has caused huge financial losses and destruction of life, property and environment. The monsoon is thought to strengthen as a result of increased temperatures, producing increased precipitation. We are testing this idea in a preliminary study of the monsoon variability during the Late Pliocene. We analyzed 10 samples taken from Site U1443 of IODP Expedition 353, which is located on the southeastern edge of the Bay of Bengal on the Ninetyeast Ridge, approximately 5° north latitude from the equator. A transfer function was used to estimate salinity levels of the Bay of Bengal during the Pliocene using planktic foraminifera assemblages contained in these samples. Preliminary ages of the samples were derived using biochronology and range from 3.302 Ma to 3.267 Ma. Thus, these samples capture the short-lived M2 glaciation event around ∼3.3 Ma. This cooling event may have weakened the Indian monsoon, as seen in structural changes in the assemblage with increased contributions from taxa likely to dwell in higher salinity environments during M2. Typically during a monsoon event we observed lower salinities due to high levels of precipitation and concomitant freshwater runoff from surrounding terrestrial environments. If our age model is correct, then we observe an overall increase in salinity moving up the section that is indicative of a weakening of the Indian monsoon.
Year of Publication: 2017
Research Program: IODP Integrated Ocean Drilling Program
IODP2 International Ocean Discovery Program
Key Words: 12 Stratigraphy, Historical Geology and Paleoecology; Bay of Bengal; Cenozoic; Expedition 353; IODP Site U1443; Indian Ocean; International Ocean Discovery Program; Neogene; Ninetyeast Ridge; Paleosalinity; Pliocene; Tertiary
Coordinates: N052300 N052301 E0902142 E0902142
Record ID: 2017078095
Copyright Information: GeoRef, Copyright 2019 American Geosciences Institute. Reference includes data supplied by the Geological Society of America, Boulder, CO, United States